Process for removing crimp from polyester filamentary tow



Jan. 21,19 9 Ff. s. E MS ET A1. 3,423,501

PROCESS FOR REMOVING CRIMP FROM POLYESTER FILAMENTARY TQW Filed Dec. 25; 1964 United States Patent 2 Claims ABSTRACT OF THE DISCLOSURE A process for decrimping crimped polyester tow by:

(1) Heating the tow to from about 65 to 80 C.,

(2) Drawing the tow to at least 150% of its uncrimped length in an inert bath maintained at from 76 to 100 C., and

(3) Drying the tow to less than about 1% moisture.

SPECIFICATION This invention relates to the processing of continuous, synthetic filamentary tow and more particularly to a process for removing crimp from synthetic filamentary tow which has been mechanically crimped.

It is well known in the textile industry to crimp tow comprising many thousands of filaments to facilitate inprocess handling of the filaments as a contiguous entity and to provide for interfilamentary cohesion in textile processing after the tow has been cut to staple or broken to sliver. The mechanically induced crimp of some synthetic fibers is easily removed; often the crimp fails even to survive the complete textile process in which it is designed to contribute fiber-to-fiber cohesiveness. In the condensation polymers such as nylons and polyesters, the tendency to heat-set in any artificially-induced configuration contributes to good crimp durability in normal processing.

However, some fiber uses, notably the fabrication of pile fabrics, require a fiber having no crimp at all. One obvious method to obtain such a product is simply to bypass the initial crimping step, leaving the tow in its as-produced straight configuration. For economical inventory, however, it has been found desirable to stock only the crimped product and to use the material as supply for the fiber uses requiring no-crimp tow. This enables the maintenance of an inventory of only the major item (product with crimp) with the resultant savings realized from storage space and associated cost.

Accordingly, it is an object of this invention to provide a novel process for decrimping crimped tow. A further object is to provide a novel process for decrimping crimped tow composed of condensation polymer filaments. Other objects will become apparent from the description hereinafter.

The objects of this invention are accomplished, in general, by a process which comprises preheating a condensation polymer tow to a temperature in the range of 65 C. to 80 C., drawing the tow to at least 150% of its uncrimped length in a bath maintained at 76 C. to 100 C. and thereafter drying the tow to a moisture content of less than 1% by weight. Preferably, the tow is drawn from about 200% to about 250% of its uncrimped length.

The accompanying schematic drawing further illustrates the novel process of this invention and apparatus which can be utilized to accomplish the novel process. In the single figure a crimped condensation polymer tow 10, from a source not shown, is advanced by feed rolls 12 or bars under rolls 14 in preheating bath 16, which 3,423,501 Patented Jan. 21, 1969 is maintained at a temperature in the range of 65 C. to C. The tow thenpasses into spray-drawing enclosure 18, in which are positioned a plurality of sprays 20 which constantly bathe condensation polymer tow 10 with an aqueous medium, heated to and maintained at from about 96 C. to about 100 C. Draw rolls 22 are driven at a surface speed sufficiently greater than that of feed rolls 12 to provide the required degree of draw in spraydrawing enclosure 18. By means of rolls 24 and 26, condensation polymer tow 10 is deposited on endless belt 28 and passes through continuous circulating-air dryer-relaxer 30, which is adjusted to operate at a suitable drying temperature such that the moisture content of condensation polymer tow 10 is reduced to less than 1% and the dry-heat shrinkage is also reduced to the desired level. The decrimped tow 32 can then be packed in carton 34 and stored until needed. Alternatively, the decrimped tow 32 could be wound on a ball warper (not shown).

The following example is illustrative of the invention but not in limitation thereof. All parts and percentages are by weight unless otherwise indicated.

Example Three-denier-per filament polyester tow of 450,000 total denier comprising a copolymer of 98% ethylene terephthalate and 2% ethylene sulfoisophthalate (the copolymer being made in accordance with the process of US. Patent No. 3,018,272) is prepared by a process substantially as described in US. Patent No. 2,918,346. The polyester tow is then crimped in a conventional stufiing box crimper similar to that described in US. Patent No. 2,734,794 and packed in shipping cartons for storage.

Two cartons of tow such as described above are decrimped by the following procedure: Using the apparatus shown in the accompanying drawing, a carton of tow is positioned at the feed end (left side) and threaded through feed rolls 12, into preheating bath 16, spraydrawing enclosure 18 and draw rolls 22. The tow is laid on the belt of a continuous belt (28) dryer-relaxer 30 in which it is dried by air at the temperature indicated in the table below.

Conditions used and properties of the crimped tow and of the decrimped tow are also given in the table. By crimp takeup is meant the percent loss in length due to crimp when a length of tow loaded with 0.121 gram per denier is unloaded and allowed to retract. By dry heat shrinkage is meant the percent loss in length which occurs on heating the tow in dry air at 193 C. for 30 minutes.

TABLE Carton No. 1 Carton N o. 2

Supply Decrimped Supply Decrimped Properties Denier per filament Tenacity (g.p.d.) 2. ngation (percent) 33. Dry heat shrinkage (percent) 4. Crimp takeup 9 Process condition Draw ratio 83. 3 Inpnt 36.4 Preheatmg bath temperature Feed roll section temperature C.) Spray-drawing enclosure temperature C.) Draw roll section temperature 80 80 Circulating-air dryer-relaxer temperature C.)

The crimp take-up measurements are an indication of the decrimping accomplished and the figures for the eX- ample hereinbefore clearly illustrate that the tow was in fact decrimped.

The present invention has made possible the decrimping of a crimped condensation polymer tow which is the equivalent of tow which has never been crimped in end uses requiring a tow with zero crimp. In fact, it is surprising that tow with essentially no crimp can successfully be laid on the continuous belt in the circulating-air dryer-relaxer or packed in cartons without the tow having lost its contiguity. In some manner not clearly understood, crimping and deerimping appear to make the tow more pliant and cohesive.

Although the example illustrates mechanically crimped tow as the starting material, it should be obvious that tow having other types of crimp can also be decrimped. For example, the spontaneous crimp illustrated in US. Patent No. 3,050,821 and the random curvilinear crimp shown in US. Patent No. 3,055,080 can also be used as starting materials. Additionally, it should be apparent that the tow could compose filaments made of any desired condensation polymers, such as the nylons and the polyesters. The tow can have a total denier as is desired, tows having a total denier of from about 400,000 to about 500,000 have been found to be convenient.

It will be apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof. and therefore it is not intended to be limited except as indicated in the appended claims.

What is claimed is:

1. The process of decrimping polyester filaments which comprises preheating a tow of crimped filaments to a temperature in the range of from about 65 C. to about 80 C., drawing said tow to at least 150% of its uncrimped length while passing it through an inert aqueous bath maintained at a temperature of from about 96 C. to about 100 C., and drying said tow to less than about 1% moisture, by weight, whereby the resulting tow is free from crimp.

2. The process of claim 1 wherein said tow is drawn to from 200% to 250% of its uncrimped length.

References Cited UNITED STATES PATENTS 3,129,485 4/1964 Shattuck 2872 3,176,374 4/1965 Kinnear 264-290 3,259,681 6/1966 Bull et al. 264290 JULIUS FROME, Primary Examiner.

A. H. KOECKERT, Assistant Examiner.

US. Cl. X.R. 

